The invention relates to enhanced oil recovery (EOR). In practical terms, EOR relates to different techniques applied for the purpose of recovering as much oil from the underground as possible. A problem related to oil recovery in general is that a significant part of the oil remains in the underground when applying conventional recovery methods. Such methods may include water and gas flooding to keep the pressure high in the reservoir. In order to increase the amount of oil recovered from the underground, different techniques have been developed to increase the amount of oil recovered from already addressed reservoirs.
The conventionally applied techniques vary significantly in complexity, depending on many different factors including e.g. type of oil, the structure and the type of the underground formation, logistics, climate, amount of oil accessible from the well, etc.
The present invention relates to a specific type of oil recovery, namely the type of recovery in which the recovery is aided by the application of enzymes.
U.S. patent application U.S. 2008/0115945 A1 describes a method for recovery of hydrocarbons in a subterranean formation by a dedicated application of enzymatic fluid. The fluid is injected into the formation by adding it directly to the pump. This is followed by a soaking period in the reservoir, and then by injecting either water or steam into the formation, again followed by a soaking period. Finally, recovery of deposits follows. Optionally, the enzymatic fluid is heated to at least 80° C. prior to injection.
A problem related to the above mentioned prior art is that such EOR method may become relatively expensive in different ways. A particular problem in relation to the above-mentioned techniques is that enzymes are relatively expensive and that the increased recovery obtained may be relatively low, when compared to the cost related to the applied enzymes and the applied recovery method.